F. A. Per ret — Lava Eruption of Stromboli. 459 



explosion took place under diametrically opposite conditions, 

 some hours after a copious outflow, following a temporary ces- 

 sation, but it is probable nevertheless that obstruction by col- 

 lapse was, in both cases, the determing cause. 



The explosion of Nov. 13 at 9.15 a. m. was sudden, power- 

 ful, but remarkably superficial in its nature, and without seis- 



Fio. 8. 



Fig. 8. First phase of the great explosion on Nov. 13, seen from 

 S. Vincenzo. 



mic effects, sending rapidly upward a dense, ball-headed cauli- 

 flower cloud of detritus of which a shower of large but light- 

 weight scoriae fell at S. Vincenzo in from five to six minutes 

 after the explosion. In ascending the mountain directly after- 

 ward, the detritus was found in masses of constantly increasing 



Am. Jour Sci. 

 82 



-Fourth Series, Vol. XLT.I, No. 252. — December, 1916. 



